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NASA NTRS2023

SelenITA: A Dual Point Lunar Mission to Characterize the Near Surface Dust and Electromagnetic Plasma Environment

SelenITA is a dual CubeSat mission that will provide the first multi-point dust, plasma, and magnetic field measurements in lunar orbit. This mission will advance the understanding of the electromagnetic space environment at the Moon in support of the Artemis program, exploration, and the geosciences. Here we present the science rationale motivating the mission. The candidate mission science objectives include: (1) constrain the origins of crustal magnetic fields; (2) determine the nature of plasma interactions with crustal magnetic fields; (3) characterize plasma waves and turbulence at the Moon; (4) characterize the lunar surface electric potential in varying plasma environments; (5) constrain the composition, thermal state, and structure of the lunar upper mantle and crust; (6) characterize the ionizing radiation in lunar orbit; and lastly, (7) determine the density of the dust exosphere as a function of latitude, longitude, and altitude, including the lunar polar space environment. The measurement requirements include simultaneous two-point observations of the 3-component vector magnetic field, plasma distribution (flux, energy, density, temperature), and single-point observations of energetic particles (protons, electrons, gamma rays), and dust. These measurements are important because it helps us understand how future astronauts, robots, and space hardware will live and work on the lunar surface.

space weather↗
NASA NTRS2023

SelenITA: A Dual Point Lunar Mission to Characterize the Near Surface Dust and Electromagnetic Plasma Environment

SelenITA is a dual CubeSat mission that will provide the first multi-point dust, plasma, and magnetic field measurements in lunar orbit. This mission will advance the understanding of the electromagnetic space environment at the Moon in support of the Artemis program, exploration, and the geosciences. Here we present the science rationale motivating the mission. The candidate mission science objectives include: (1) constrain the origins of crustal magnetic fields; (2) determine the nature of plasma interactions with crustal magnetic fields; (3) characterize plasma waves and turbulence at the Moon; (4) characterize the lunar surface electric potential in varying plasma environments; (5) constrain the composition, thermal state, and structure of the lunar upper mantle and crust; (6) characterize the ionizing radiation in lunar orbit; and lastly, (7) determine the density of the dust exosphere as a function of latitude, longitude, and altitude, including the lunar polar space environment. The measurement requirements include simultaneous two-point observations of the 3-component vector magnetic field, plasma distribution (flux, energy, density, temperature), and single-point observations of energetic particles (protons, electrons, gamma rays), and dust. These measurements are important because it helps us understand how future astronauts, robots, and space hardware will live and work on the lunar surface.

space weather↗
NASA NTRS2010

Lunar Atmosphere and Dust Environment Explorer Integration and Test

Integration and test (I&T) of the Lunar Atmosphere and Dust Environment Explorer (LADEE) is presented. A collaborative NASA project between Goddard Space Flight Center and Ames Research Center, LADEE's mission is to explore the low lunar orbit environment and exosphere for constituents. Its instruments include two spectrometers, a dust detector, and a laser communication technology demonstration. Although a relatively low-cost spacecraft, LADEE has I&T requirements typical of most planetary probes, such as prelaunch contamination control, sterilization, and instrument calibration. To lead to a successful mission, I&T at the spacecraft, instrument, and observatory level must include step-by-step and end-to-end functional, environmental, and performance testing. Due to its compressed development schedule, LADEE I&T planning requires adjusting test flows and sequences to account for long-lead critical-path items and limited spares. A protoflight test-level strategy is also baselined. However, the program benefits from having two independent but collaborative teams of engineers, managers, and technicians that have a wealth of flight project experience. This paper summarizes the LADEE I&T planning, flow, facilities, and probe-unique processes. Coordination of requirements and approaches to I&T when multiple organizations are involved is discussed. Also presented are cost-effective approaches to I&T that are transferable to most any spaceflight project I&T program.

Wright, Michael R.↗
NASA NTRS2011

What Will LADEE Tell Us About the Lunar Atmosphere?

The only species that have been confirmed in the lunar exosphere are Na, K, Ar, and He. However, models for the production and loss of lunar regolith-derived exospheric species from source processes including micrometeoroid impact vaporization, sputtering, and, for Na and K, photon-stimulated desorption, predict a host of other species should exist in the lunar exosphere. Assuming that loss processes are limited to ballistic escape, photoionization, and recycling to the surface, we have computed column abundances and compared them to published upper limits from the Moon and to detected abundances from Mercury. Our results suggest that available measurements often do not constrain models, and underline the need for improved spectroscopic measurements of the lunar exosphere. Such investigations are planned by the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft. Our calculations indicate that LADEE measurements promise to make definitive observations or set stringent upper limits for all regolith-driven exospheric species because of their favorable signal to noise ratio. Our models, along with LADEE observations, will constrain assumed model parameters for the Moon, such as sticking coefficients, source processes, and velocity distributions.

FROM↗
NASA NTRS2017

Absence of a Detectable Lunar Nanodust Exosphere During a Search with LRO's LAMP UV Imaging Spectrograph

The Lyman-Alpha Mapping Project (LAMP) UV spectrograph on board the Lunar Reconnaissance Orbiter (LRO) performed a campaign to observe the Moon's nanodust exosphere, evidence for which was provided by the Lunar Atmosphere and Dust Environment Explorer (LADEE) Ultraviolet and Visible Spectrometer (UVS) during the 2014 Quadrantid meteoroid stream. These LADEE/UVS observations were consistent with a nanodust exosphere modulated by meteoroid impacts. LRO performed off-nadir maneuvers around the peak of the 2016 Quadrantids, in order to reproduce, as closely as possible, the active meteoroid environment and observing geometry of LADEE/UVS. We analyzed LAMP spectra to search for sunlight backscattering from nanodust. No brightness enhancement attributable to dust, of any size, was observed. We determine an upper limit for dust column concentration of ~10(^ 5) sq. cm for grains of radius ~25 nm, and an upper limit for dust column mass of ~10 11 g sq. cm, nearly independent of grain size for radii <100 nm.

Spectrograph↗
NASA NTRS2010

Lunar Atmosphere and Dust Environment Explorer Integration and Test

The Lunar Atmosphere and Dust Environment Explorer (LADEE) is a NASA collaborative flight project to explore the lunar exosphere. It is being developed through a unique partnership between NASA's Ames Research Center (ARC) and Goddard Space Flight Center (GSFC). Each center brings its own experience and flight systems heritage to the task of integrating and testing the LADEE subsystems, instruments, and spacecraft. As an "in-house" flight project being implemented at low-cost and moderate risk, LADEE relies on single-string subsystems and protoflight hardware to accomplish its mission. Integration and test (l&T) of the LADEE spacecraft with the instruments will be performed at GSFC, and includes assembly, integration, functional testing, and flight qualification and acceptance testing. Due to the nature of the LADEE mission, l&T requirements include strict contamination control measures and instrument calibration procedures. Environmental testing will include electromagnetic compatibility (EMC), vibro-acoustic testing, and thermal-balance/vacuum. Upon successful completion of spacecraft l&T, LADEE will be launched from NASA's Wallops Flight Facility. Launch of the LADEE spacecraft is currently scheduled for December 2012.

Wright, Michael R.↗
NASA NTRS2015

Understanding Temporal and Spatial Variability of the Lunar Helium Atmosphere Using Simultaneous Observations from LRO, LADEE, and ARTEMIS

Simultaneous measurements of helium in the exosphere of the Moon are made from the Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP) and the Lunar Atmosphere and Dust Environment Explorer (LADEE) Neutral Mass Spectrometer (NMS) through the entire 5-month span of the LADEE mission. In addition, the ARTEMIS mission monitored the solar wind alpha particle flux to the Moon. Modeling the lunar helium exosphere, we relate the LAMP polar observations to the LADEE equatorial observations. Further, using the ARTEMIS alpha flux in the Monte Carlo model reproduces the temporal variations in helium density. Comparing the LAMP data to the LADEE data shows excellent agreement. Comparing those with the ARTEMIS data reveals that the solar wind alpha flux is the primary driver to variability in the helium exosphere throughout the LADEE mission. Using a decay time for exospheric helium of 5 days, we determine that the solar wind contributes 64 +/- 5% of the helium to the lunar exosphere. The remaining 36 +/- 5% is presumed to come from outgassing of radiogenic helium from the interior of the Moon. Furthermore, the model reproduces the measurements if 63 +/- 6% of the incident alpha particles are converted to thermalized helium atoms through the interaction between the alphas and the lunar surface. However, these values are dependent on both inferred source rates from LAMP and LADEE observations and on the assumed time constant of the exospheric decay rate.

Moon↗
NASA NTRS2005

A Dynamic Fountain Model for Lunar Dust

During the Apollo era of exploration it was discovered that sunlight was scattered at the terminators giving rise to horizon glow and streamers above the lunar surface. This was observed from the dark side of the Moon during sunset and sunrise by both surface landers and astronauts in orbit. These observations were quite unexpected, as the Moon was thought to be a pristine environment with a negligible atmosphere or exosphere. Subsequent investigations have shown that the sunlight was most likely scattered by electrostatically charged dust grains originating from the surface. It has since been demonstrated that this dust population could have serious implications for astronomical observations from the lunar surface. The lunar surface is electrostatically charged by the Moon s large-scale interaction with the local plasma environment and the photoemission of electrons due to solar ultra-violet (UV) light and X-rays. The like-charged surface and dust grains then act to repel each other, such that under certain conditions the dust grains are lifted above the surface. We present a dynamic fountain model which can explain how sub-micron dust is able to reach altitudes of up to approximately 100 km above the lunar surface. Previous static dust levitation models are most applicable to the heavier micron-sized grains in close proximity proximity to the surface, but they cannot explain the presence of extremely light grains at high altitudes. If we relax the static constraint applied to previous models, and instead assume that the grains are in constant motion (under the action of dynamic forces), a new picture emerges for the behavior of sub-micron lunar dust.

Stubbs, T. J.↗
NASA NTRS2011

Metallic Species, Oxygen and Silicon in the Lunar Exosphere: Upper Limits and Prospects for LADEE Measurements

The only species that have been continued in the lunar exosphere are Na, K, Ar, and He. Models for the production and loss of lunar regolith-derived exospheric species from source processes including micrometeoroid impact vaporization, sputtering. and, for Na and K, photon-stimulated desorption, predict a host of other species should exist in the lunar exosphere. Assuming that loss processes are limited to ballistic escape and recycling to the surface, we have computed column abundances and compared them to published upper limits from the Moon and to detected abundances from Mercury. Only for Ca do the available measurements show a clear deficiency compared to the model estimates. This result suggests the importance of loss processes not included in the model, such as the possibility of gas-to-solid phase condensation during micrometeoroid impacts or the formation of stable metallic oxides, and underlines the need for improved spectroscopic measurements of the lunar exosphere. Simulations of the neutral mass (NMS) and visible/ultraviolet spectrometry (UVS) investigations planned by the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft are presented. Our calculations indicate that LADEE measurements promise to make definitive observations or set stringent upper limits for all regolith-driven exospheric species. Our models, along with LADEE observations, will constrain assumed model parameters for the Moon, such as sticking coefficients, source processes. and velocity distributions.

Sarantos, Menelaos↗
NASA NTRS2016

How Surface Composition and Meteoroid Impacts Mediate Sodium and Potassium in the Lunar Exosphere

Despite being trace constituents of the lunar exosphere, sodium and potassium are the most readily observed species due to their bright line emission. Measurements of these species by the Ultraviolet and Visible Spectrometer (UVS) on the Lunar Atmosphere and Dust Environment Explorer (LADEE) have revealed unambiguous temporal and spatial variations indicative of a strong role for meteoroid bombardment and surface composition in determining the composition and local time dependence of the Moon's exosphere. Observations show distinct lunar day (monthly) cycles for both species as well as an annual cycle for sodium. The first continuous measurements for potassium show a more repeatable variation across lunations and an enhancement over KREEP (Potassium Rare Earth Elements and Phosphorus) surface regions, revealing a strong dependence on surface composition.

Colaprete, A.↗
NASA NTRS2019

Meteoroids at the Moon: Orbital Properties, Surface Vaporization, and Impact Ejecta Production

We use a dynamical model to characterize the monthly and yearly variations of the lunar meteoroid environment for meteoroids originating from short and long‐period comets and the main‐belt asteroids. Our results show that if we assume the meteoroid mass flux of 43.3 tons per day at Earth, inferred from previous works, the mass flux of meteoroids impacting the Moon is 30 times smaller, approximately 1.4 tons per day, and shows variations of the order of 10% over a year. The mass flux difference is due to the combined effect of the smaller cross‐section of the Moon (factor of 13.46) and Earth's larger gravitational focusing (factor of 2–2.5). The lunar surface is vaporized by these impactors at an average impact vaporization flux of 11.6 × 10−16 g·cm−2·s−1, providing a significant source for the rarefied lunar exosphere. Our model predicts acceptable vaporization rates and reproduces the local time dependence of observations of the dust ejecta cloud, measured by the Lunar Dust Experiment on board NASA's Lunar Atmosphere and Dust Environment (LADEE) satellite. However, the predicted density of the lunar ejecta cloud is four orders of magnitude larger than reported values by LADEE. This discrepancy might be attributed to a much lower yield from meteoroid impacts on fluffy lunar regolith and/or a lower detection efficiency of the LADEE dust detector. We suggest an upper limit of 30 cm per million years for the soil gardening rate from small meteoroids.

Petr Pokorny↗
NASA NTRS2010

The Lunar Atmosphere and Dust Environment Explorer (LADEE) Mission

The Lunar Atmosphere and Dust Environment Explorer (LADEE) is a Lunar science orbiter mission currently under development to address the goals of the National Research Council decadal surveys and the recent "Scientific Context for Exploration of the Moon" (SCEM) [1] report to study the pristine state of the lunar atmosphere and dust environment prior to significant human activities. LADEE will determine the composition of the lunar atmosphere and investigate the processes that control its distribution and variability, including sources, sinks, and surface interactions. LADEE will also determine whether dust is present in the lunar exosphere, and reveal the processes that contribute to its sources and variability. These investigations are relevant to our understanding of surface boundary exospheres and dust processes throughout the solar system, address questions regarding the origin and evolution of lunar volatiles, and have potential implications for future exploration activities. LADEE employs a high heritage science instrument payload including a neutral mass spectrometer, ultraviolet spectrometer, and dust sensor. In addition to the science payloads, LADEE will fly a laser communications system technology demonstration that could provide a building block for future space communications architectures. LADEE is an important component in NASA's portfolio of near-term lunar missions, addressing objectives that are currently not covered by other U.S. or international efforts, and whose observations must be conducted before large-scale human or robotic activities irrevocably perturb the tenuous and fragile lunar atmosphere. LADEE will also demonstrate the effectiveness of a low-cost, rapid-development program utilizing a modular bus design launched on the new Minotaur V launch vehicle. Once proven, this capability could enable future lunar missions in a highly cost constrained environment. This paper describes the LADEE objectives, mission design, and technical approach.

Spremo, Stevan↗
NASA NTRS2011

On the Role of Dust in the Lunar Ionosphere

Evidence suggests that electron concentrations above the dayside lunar surface can be significantly higher than expected from either the photo-ionization of exospheric neutrals or any other well-known process. The Luna 19 mission performed dual-frequency radio occultation experiments in order to determine electron column concentrations above the lunar limb as a function of tangent height (shown in the figure below), The resulting electron concentration profiles surprisingly indicated a peak of approx.500-1000/cu cm and scale heights of approx. 10-30 km. It has been suggested that electrically charged exospheric dust could contribute to these electron cnhancemcnts2 , Here we describe how to estimate the electrons produced by photo-charged dust, which is then used to predict electron concentrations from exospheric dust distribution models that are based on the "excess brightness" observed in Apollo 15 coronal photographs. The results indicate that radio occultation measurements likely provide a valuable perspective on the role of dust in the lunar environment.

Stubbs, Timothy J.↗
NASA NTRS2011

Neutral Mass Spectrometer (NMS) for the Lunar Atmosphere and Dust Environment Explorer (LADEE) Mission

The Lunar Atmosphere and Dust Environment Explorer (LADEE) mission currently scheduled for launch in early 2013 aboard a Minotaur V will orbit the moon at a nominal periselene of 50 km to characterized the lunar atmosphere and dust environment. The science instrument payload includes a neutral mass spectrometer as well as an ultraviolet spectrometer and a dust detector. Although to date only He, Ar-40, K, Na and Rn-222 have been firmly identified in the lunar exosphere and arise from the solar wind (He), the lunar regolith (K and Na) and the lunar interior (Ar-40, Rn-222), upper limits have been set for a large number of other species, LADEE Neutral Mass Spectrometer (NMS) observations will determine the abundance of several species and substantially lower the present upper limits for many others. Additionally, LADEE NMS will observe the spatial distribution and temporal variability of species which condense at nighttime and show peak concentrations at the dawn terminator (e,g, Ar-40), possible episodic release from the lunar interior, and the results of sputtering or desorption processes from the regolith. In this presentation, we describe the LADEE NMS hardware and the anticipated science results.

Collier, Michael R.↗
NASA NTRS2015

The Use of Standards on the LADEE Mission

The Lunar Atmosphere Dust Environment Explorer (LADEE) was a small explorer class mission that launched Sept 7, 2013 and successfully de-orbited and impacted the moon's surface on April 17, 2014. The spacecraft was the first to launch from a Minotaur 5 and was the first deep space mission to launch from the Wallops flight facility. Figure 1 shows the famous image of a frog unlucky enough to be launched from the facility at the same time as LADEE. The science mission for the spacecraft was to determine the density, composition and variability of the lunar exosphere. In addition, it performed a first-of-a-kind demonstration of laser-based communications from deep space that exhibited a record downlink rate of 622 megabits per second from the moon. In order to perform the lunar dust surveys, the spacecraft was placed in a retrograde equatorial orbit with periapsis between 20 and 60 kilometers. The mission was granted an extension in which final science surveys were performed at altitudes as low as 2 kilometers over the moon's surface. The cadence for spacecraft operations was demanding: the moon's highly inhomogeneous gravity field distorted the orbit, the regular maneuvers were subject to strict payload-induced pointing requirements, and there were periodic attitude changes to keep the spacecraft thermally safe. This led to a need for high reliability in the operation of the spacecraft while obeying strict budget and schedule guidelines.

Standards↗
NASA NTRS2016

An Examination of LADEE UVS Spectral Variability Associated with the Geminid Meteor Shower

The Lunar Atmosphere and Dust Environment Explorer (LADEE) was an orbital lunar science mission designed to address the goals of the 2003 National Research Council decadal survey, the Lunar Exploration Analysis Group Roadmap, and the “Scientific Context for Exploration of the Moon” (SCEM) report, and has been recommended for execution by the 2011 Planetary Missions Decadal Survey. The LADEE mission goal was to determine the composition of the lunar atmosphere and investigate the processes that control its distribution and variability, including sources, sinks, and surface interactions. LADEE monitored variations in known gasses, such as sodium, potassium, argon and helium, and searched for other, as-yet-undetected gasses of both lunar and extralunar origin. LADEE also examined whether dust is present in the lunar exosphere, and revealed the processes that contribute to its sources and variability. LADEE launched September 6, 2013, entered lunar orbit on October 6, 2013 and operated until April 17, 2014. Examined here are spectral variability at around the time of the Geminid meteor shower (at around December 13-14, 2014). UVS made standard limb observations at the Sunrise and Sunset terminators, as well as observation looking anti-sun on the dark side of the moon (the so called “Sodium-Tail” observation type). The before, during and after spectra are compared to look for variability in line emissions.

Ultraviolet and Visible Spectrometer (UVS)↗
NASA NTRS2012

A Small, Remotely Operated, Coronagraph located at Small Observatory to obtain Frequent Low-cost Remote Observations of the Lunar Exosphere

The sodium in the lunar exosphere is a marker for the study of the lunar exosphere because the sodium possesses two strong resonance transitions from the ground state whose wavelengths fall in the visible spectrum near 590 nm. Emissions at these wavelengths are thus, observable from Earth. Observations have shown that the exosphere responds in a complex way to the external processes (impact vaporization, sputtering, and photon stimulated desorption) that weather the lunar regolith to produce the sodium (Sarantos et aI., Icarus, 205, 2010). Unraveling the sodium production allows us to study the processes that weather the regolith. Obtaining the extensive time sequence of observations required to unravel the sources of sodium using conventional observatories is impractical, and too expensive. Effectively imaging the lunar sodium exosphere close to the Moon requires an off-axis rejection of scattered light that can only be obtained with a coronagraph sited at an observatory dedicated to remote robotic observing (the Winer Observatory in Sonoita Arizona) that can obtain the quality and quantity of lunar sodium observations needed to answer these questions, and at modest cost. The design uses Commercial Off the Shelf Technology (COTS). We are working to begin routine the observations before the launch of the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission.

Morgan, Thomas↗
NASA NTRS2013

First Results from NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE)

As of early August, 2013, the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission is scheduled for launch on a Minotaur V rocket from Wallops Flight Facility during a five-day launch period that opens on Sept. 6, 2013 (early Sept. 7 UTC). LADEE will address 40 year-old mysteries of the lunar atmosphere and the question of levitated lunar dust. It will also pioneer the next generation of optical space communications. LADEE will assess the composition of the lunar atmosphere and investigate the processes that control its distribution and variability, including sources, sinks, and surface interactions. LADEE will also determine whether dust is present in the lunar exosphere, and reveal its sources and variability. These investigations are relevant to our understanding of surface boundary exospheres and dust processes occurring at many objects throughout the solar system, address questions regarding the origin and evolution of lunar volatiles, and have potential implications for future exploration activities. Following a successful launch, LADEE will enter a series of phasing orbits, which allows the spacecraft to arrive at the Moon at the proper time and phase. This approach accommodates any dispersion in the Minotaur V launch injection. LADEE's arrival at the moon in early October. The spacecraft will approach the moon from its leading edge, travel behind the Moon out of sight of the Earth, and then re-emerge and execute a three-minute Lunar Orbit Insertion maneuver. This will place LADEE in an elliptical retrograde equatorial orbit with an orbital period of approximately 24 hours. A series of maneuvers is then performed to reduce the orbit to become nearly circular with a 156-mile (250- kilometer) altitude. Spacecraft checkout and science instrument commissioning will commence in early-October and will nominally span 30 days but can be extended for an additional 30 days in the event of contingencies. Following commissioning, the 100-day Science Phase is performed at an orbit with periapsis between 20-60 km. This orbit must be constantly managed due to the Moon's highly inhomogeneous gravity field. During the Science Phase, the moon will rotate more than three times underneath the LADEE orbit. LADEE employs a high heritage instrument payload: a Neutral Mass Spectrometer (NMS) from Goddard Space Flight Center, an Ultraviolet/Visible Spectrometer (UVS) from Ames Research Center, and a dust detection experiment (LDEX) from the University of Colorado/LASP. It will also carry the Lunar Laser Communications Demonstration (LLCD) as a technology demonstration. The LLCD is funded by the Human Exploration Operations Mission Directorate (HEOMD), managed by GSFC, and built by the MIT Lincoln Lab. Contingent upon LADEE's successful lunar orbit insertion and checkout, we will report the early results from the science investigations.

Moon↗